Clinical and animal experiments have indicated that the posterior parietal cortex of humans and monkeys is important for visual-motor integration including the coordinate transformations required for these functions. In these experiments the role of this brain region in visual-motor and spatial functions will be examined with primarily neurophysiological techniques, but will also include psychophysical, anatomical and computational approaches. The proposal has two specific aims. 1) To examine in detail the lateral intraparietal area (LIP), a cortical field located in the lateral bank of the intraparietal sulcus which we have found to be involved in the processing of saccadic eye movements. We will examine in detail our recent finding of an eye-position dependent tuning of these neurons for saccades made to locations in head-centered coordinate space. We will also examine a newly discovered class of neurons in this area that hold in short-term memory intended eye movements and thus appear to be involved in motor planning. We will examine the functional and anatomical organization of this area using electrophysiological mapping, micro-stimulation and neuroanatomical tracing techniques. We will examine the effects of ibotenic acid induced lesions of area LIP on saccadic eye movements. Preliminary experiments show a deficit in saccades to remembered locations but not to constantly present visual targets. This deficit has an orbital position dependence and is transient lasting only a few days. In conjunction with these experiments, we will study the metrics of saccades made to remembered spatial locations in monkeys and humans. Initial experiments indicated that the neural representation of remembered locations in visual space used for saccades is highly distorted with hypermetric saccades occurring for upward targets and hypometric saccades occurring for downward targets. 2) In a second series of experiments we will continue to examine the coding of visual targets in head-centered coordinate space by light-sensitive neurons in area 7a of the posterior parietal cortex. We will examine the possible role of proprioception in this spatial tuning by sectioning the ophthalmic branch of the trigeminal nerve which is the sole source of proprioceptive inputs from the eye muscles. We will also examine the role of head position in the spatial tuning of these neurons; i.e., we will determine if the cells are actually coding target locations in a body-centered spatial frame. Finally, we will study the time- course of the integration of eye position and visual signals by these cells and compare it to the time-course for perceptual recalibration for spatial position in humans.